Calculation of kidney function and definition of
CKD
The estimated glomerular filtration rate (GFR)
was calculated with the Modification of Diet in Renal
Disease (MDRD) Study equation [GFR = 186.3 × (serum
creatinine in mg/dl)-1.154× (age)-0.203× (0.742 if female)]
[10]. CKD was defined as a GFR less than 60
ml/min per1.73 m2. This range corresponds to stage 3
or higher CKD by the National Kidney Foundation's
classification scheme and helps identify individuals
with clinically significant CKD [12].